Electric condenser



July 31, 1945. c. E. MAITLAND 7 ELECTRIC CONDENSER Filed April 15, 1943 Z2 CHILEMMTLAND 20 INVENTOR.

fy daflarif ATTORNEY Patented July 31, 1945 ELECTRIC CONDENSER Cyril Edmund Maitland, Harrow; England, assigno'r to The Hartford National Bank and Trust Company, Hartford, Coma, as trustee Application April 15, 1943, Serial No. 483,203

In Great Britain March 2'1, 1942 4 Claims.

This invention relates to electrical condensers and more particularly to adjustable electrical condensers of the type in which the adjustment of the capacity is eflected by rotation of a control shaft in relation to a fixed nut or by rotation of a nut in relation to a fixed shaft, the movement of the shaft or nut as the case may be producin a relative displacement of the electrode plates of the condenser by rotation and/or by longitudinal displacement. Such condensers are widely. used as pre-set or trimmer condensers and in such use it is necessary that once these condensers have been adjusted to their desired capacity value no further displacement of the adjusting means should occur due to shock, vibration and/or by inadvertent handling.

According to the present invention the. rotatable control means is locked by means of two helical springs, the internal diameter of which is slightly smaller than the shaft which they embrace. Each of the springs is anchored at one end and so arranged that rotation of the control means in one direction tends to tighten one spring which consequently opposes rotation in that direction, while rotation in the other direction tends to tighten the other spring which consequently prevents rotation in the other direc-- tion. The free end of each spring is constituted as or provided with a projecting lever which can be manipulated'to loosen the spring to permit rotation of thecontrol means for any desired adjustment. Conveniently springs of the same pitch are mounted side by side with their adjacent ends anchored.

I In many cases the rotatable control means is a threaded shaft which'carries one or more of the condenser plates so that rotation of the shaft causes movement of this plate orthese-plates in the axial direction of the shaft. Where such a threaded shaft is employed the springs are advantageously of the same helical pitch as the screw thread and are received by the screw thread. In thisway a large area of contact can behaobtained between the locking springs and the The locking springs can conveniently be anchored in diametrically opposed bosses with the levers at the free ends of the springs projecting in the spaces between the bosses.

The use of a pair of helical springs as defined above gives reliable locking while permitting ready adjustment to any desired setting. The locking means do not impede readjustment nor does their action tend to modify the adjusted position.

The invention will be further described with reference to the appended drawing in which:

Fig. 1 is a side elevation of a condenser embodying the invention,

Fig. 2 is a longitudinal section along the line 11-11 of Fig. 1. Fig. 3 is an end view of the condenser looking on the left hand end in Fig. 1 or 2 with the cap removed,

Fig. 4 is an end view of the cap as seen from the right hand end in Fig. 1 or 2.

The condenser is of the concentric type and comprises two sets of cylinders I and 2 constituting the condenser electrodes. Each set of cylinders is mounted on a corresponding end plate and each unit may conveniently be made from a light metal such as aluminum, by casting. In the example illustrated, the condenser electrodes I are stationarily mounted on an insulating sleeve 3 preferably of steatite or other low-loss material' The condenser electrodes 2 are rotatably and slidably supported on the sleeve 3 to enable the capacity of the condenser to be adjusted by varying the degree of overlap or interpenetration of the two sets of electrodes 1 and 2. r

Passing co-axially through the sleeve 3 is a metal rod 4 the left hand end of which (Fig. 2) is of greater diameter than the bore in the sleeve 3 and abuts against the adjacent end of the sleeve 3. The other end of the rod 4 is soldered to a metal cap 1 embracing the corresponding end of the sleeve 3.' In this way the rod 4 is immovably secured to the sleeve 3. The left hand end (Fig 2) of the rod] is provided with a screw thread It and terminates in stop block l5. Embracing the screw thread It are two oppositely wound helical springs l8, ll. These springs are preferably of the same pitch as the screw thread It v and of such internal diameter that they have to be expanded somewhat to embrace the screw thread and thus exert a gripping action thereon The adjacent ends l8, IQ of the springs l6, I! are anchored-in bracket members 5 which are secured to the electrode unit 2, for example by rivets 20. Alternatively, the brackets 5 could be made integrally with the electrode unit 2. In the example illustrated, the spring ends l8, I! are inserted in slots 9 in the members 5 and are secured by compressing the sides of the slots, as is apparent from Fig. 3.

The free ends 2!, 22 of the springs I6, I! extend substantially radially in the space between the two upstanding components of the brackets 5 in which the ends l8, 19 are anchored. The springs l6 I! thus constitute a nut in threaded engagement with the threaded part ll of the shaft 4. The springs exert a locking action in opposite senses so that inadvertent rotation of the nut l6, I! on the thread H is prevented. By displacement of one or both of the free ends it, 22, the nut can be released for rotation in either or both directions, thereby enabling adjustment thread ll.

of the condenser electrodes 2 in relation to the electrodes I.

To facilitate the adjustment, the icllowim: ar rangement is provided. In the threaded ana -8 ment with the thread I4 is a cap it which servec to protect and enclose the sprints it, it. This cap II is coupled with the nutll, ll by means of an internal rib II extending into the gap be tween the free ends II, 2! of the springs, as best seen from Fig. 3. Referring to Fig. 3, rotation of the cap II in clockwise direction initially causes the rib ll to engage the end 22 of the spring i1 thereby slackening the grip of this spring on the Further clockwise rotation muses the nut il, H to rotate in the same direction to sether with the brackets I and the electrode unit I. The last mentioned consequently moves to the right in Pig. 2.- Rotation in the reverse direction gives rise to corresponding movement of the elec- ,After adjustment of the stop screw H it is locked in relation to the cap II in any convenient manner, such as by running in wax II or a low-melting point alloy. The stop screw II can then be concealed by a press-in cap It. The cap II can mea ow thcireoi, u cap member sin-rounding the springs and being in separate engagement with said shaft chit mite thereon an, opposite end of each spring cnichorcd with respect to the second electrmle lam-iii the-other end of each spring being tree, cap member comprising an internalis projecting portion extending between the free ends of the springc said projecting portion engaaing the free end of one spring on imitation of the cap in one direction and enzaglnc free end of the other spring on rotation oi. time cap in the other direction.

2. In an adjustable condenser comprising two coaxial electrode units axially adiustable with respect to each other for adjusting the capacity of the condenser, rotatable control means for ad- Justina the position of the electrode units relative to each other and locking means for preventing inadvertent alteration oi. the position of the electrode units, said control and lmking means mmpriciirig a threaded shaft member rigidone electrode unit two helical iii spring: wlchomd with respect to trade send the other end oi each spring being im, a cap member surrounding said besetbyhandorbyaspannerorliketoolen--' gaging a hexagon nut formed on the outer end ofthe cap ll. .i

The electrical connection to the electrodeunit i isobtainedbymeansoftacllintegral withor securedto theunit I. Intheexample illustrated, the tags I are providedon a plate secured the springs in separate cnd rotatable enzaaement with said shaft and comprising a preset stop memmr and an internally projecting portion. said stop member limiting the movement of said cap member in one direction on said shaft and said internally projecting portion eng eins the free end of one spring on rotation of the cap in one direction and engaging the free end of the other spring on rotation of the cap member in the other direction.

' 3. In an adjustable condenser comprising two electrode units movablewith respect to each other 40 foo'adiusting the capacity of the condenser, ro-

unit I by rivets II. The connection to trodeunitlmaybederivedfronthesiifift bywayofthesprings ll, l'landthebra'cketsy Ifthecondenscristobemountedona the panel may conveniently occupy thepoaition -indicatedatllin!lg.2. Thepaneil'lisprovidedwithopeningstoreoeivethetagslandthe component may be so arasanchoring Instcadofthesprings|l,l1constitutinganut travelling on a stationary shaft the converse arrangement could be adopted: equally a separate nutcouldbeprovidedandthespringsscrveonly forlockingpurposes,

meanssecuring tatable control means for adjusting the position of the electrode units relative to each other and for locking the said electrodes to prevent inadvertent alteration of the position of the electrodes. said control and locking means comprising a threaded shaft member rigidly fixed with respect to one electrode unit, a pair of helical springs While I have described my invention by means ofspecincexamplesandinaspeclnccmbodiment for adjusting the capacity of the.

able control means for adjusting the position of the electrode units relative to each other and locking means for preventing inadvertmt altera-Y tionodthepoaitionoitheelectrodeunltasaid control'andlockingmeanscomprlaingathreaded 'on-afldlhll'tin'mm with thethreads said control and locking means comprising a threaded shaft member rigidly fixed with respect to one electrode unit, a pair-.of helical springs arranged side by side on said shaft in engagement with the threads thereof each having an oppositeend secured to the second electrode and the other end free, and means to 'rotate said springs relative to the said shaft, said means comprising a rotatable element wilti g said shaft and havin: a rib portion, said rib Portion cuisine the free end of one spring on rotation of the rotatable element in one direction and emside by side on said shaft in en 1e intends thereof with an oppo- 

